Conversion of hydrocarbon oil



J. W. GRAY CGNYERSION OF EYBEOMLRBGN OIL Juney 20, 1939.

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' .ETORNY Patented June 20, 1939 lJfNl'rln)` s'mras PATENT o-,FFICE This invention relates to the conversion of high boiling` hydrocarbon oil into lower boiling hydrof carbons suitable for motor fuel and pertains more particularly lto the processing of heavy oil such as reduced crude, heavy gas oil or an oil contain ing crude residual constituents.

Ithas heretoforebeen a practice to ,subject heavy oil stocks such as reduced crude, heavy-gas oil or other oil stocks having coke-forming tendencies 'to mild cracking treatment, ,commonly`l known as viscosity breaking treatment, controlled to produce a maximum yield of gas oil suitable for high temperature drastic cracking treatment. In some instances the temperature necessary to effect themild cracking treatment ci' the heavy oil has been accomplished .'by'v passing 'the `oil through a separate heating coil located withina furnace, and in other cases the heavy oilhas been heated to the required mild crackingtemperature by direct contact vwith more highly heated products, such as-products from a high temperature cracking operation. v

My invention isl directed to an improvement in a process of the general type last mentionedv wherein the mild cracklnglof the'heavy oil is accomplished by direct contact with highly heated products from a cracking operation.

The principal object of myinvention is to accomplish the mild cracking treatmentv of the heavy oil in al morev simple and effective manner.

A further important obje'cttof my invention is to effect the mild cracking or viscosity breaking treatment of the heavy oilin a lesser amount of equipment. .i A further important object of my invention is to obtain a greater degree of mild-cracking or viscosity-breaking treatment of heavy oil charged to the system while-minimizing coking.

More specific objects and advantages of my 40 invention will be apparent i'rom the more detailed description hereinafter. t

In accordance vwith my invention, highly heated products from a high temperature crackingoperation, processing clean condensate stock, are iniii` jected into an enlarged zone vcontaining a bodyf without being subjected to extended cracking in the enlarged zone.

'sa For a better understanding o: my. 'invention reference is now made to the accompanying drawing whichiis a diagrammaticillust'ration of an apparatus, having parts shown in section, suitable for carrying the invention into effect.

Referring to the drawing, the numeral Ill des- 5 ignates a. charging line throughwhich a clean condensate stock, amenable to high temperature ,drastic cracking treatment, forced by means of pump II to the heating coil I2.` This clean condensate stock may comprise condensate re- 10 sulting from fractionationof the cracked vapors in fractionating tower I3, in which case the cndensate is withdrawn from 'the bottom of the` tower I3- through line. Il which merges with charge line I0, `orL the chargingstock to heating 15 coil I2 mayconsist in whole or in part of clean condensate .oil from an extraneous source, in whichcase the extraneous oil is introduced into the system through line I5 formingan extension of une In. 2

The clean condensate charge during its passage through the heatingcoil I2, located'in the radiant heat section of the furnace I6, provided with burners -I 1, is rapidly heated to a high cracking temperature such asfrom 950 to 1050o F. 25 or thereabouts. l

The oil, after being heated to the desired crack ing temperature of the order'mentioned, is allowed to remain at the high temperature for a period sufficient to effect the desiredl conversion. 30 To this end the oil may be caused to pass through tube bank I1 located in the convection section-of the furnace. In some 'cases it may be desirable to complete the conversion in an enlarge'dvdiges tion chamber in which event th oil from the 3 5 furnace passes via lines I8 and I! to a reaction chamber 2| wherein the desired conversion is carried to completion. The cracked products, after undergoing the desired conversion within the furnace Il, or after 40 being completed in reaction chamber 2-I, in event the latter is employed, are passed* through transfer line 22 through a tangential inlet 26 to the bottom section of a separator and cracking chamber 23 directly below a baiiie plate 2l which is of 45 the doughnut type, having'a central opening 25. While I have shown the inletpipe '26 as being preferably tangential, this pipejmay be pointed i partially downwardly, or'upwardly, 'or if desired,

against the sidewall ot the chamber 23. 5 0

The cracked products from the transfer line 22, entering the bottom section of theseparator v23 preferably in a tangential direction, cause a rapid whirling of the products in the-bottoni of the separator 2l below the baille 2l, thus eiecting 55 a rapid separation of the vapors from the cracked residue and forcing the vapors toward the center of the chamber where they pass upwardly through the opening 25 in the baille 24, while the heavier cracked residue is forced outwardly against the wall of the chamber where it drops to the bottom of the separator and is removed therefrom through line 21 before the cracked residue is permitted to undergo extended cracking within the separator 23.

The cracked vapors liberated in the bottom section of the separator pass upwardly through the chamber in direct countercurrent contact with a relatively heavy oil, such as crude, reduced crude, heavy gas oil or other oil stocks. This heavy oil, which may be preheated to a temperature of about 500 F. or higher or which may be used at atmospheric temperature is introduced into the chamber 23 through a charge line 28 provided with a pump 29. The heavy oil, upon contacting with the hot cracked vapors, is heated to a mild cracking temperature, such as from '700 F. to 810 F. or preferably 730 to 780 F.`and is maintained within the chamber for a period sufficient to effect a substantial amlount of cracking to form a maximum yield of intermediate cycle stock suitable for high temperature cracking essential to the production of maximum yields of high anti-knock gasoline. For example, the heavy oil may be cracked within separator and cracking chamber 23 to convert from 15 to 30 -per cent into constituents below the initial boiling point of the original-charge of whichfrom 8 to 15 per cent may be within the gasoline boiling range.

heavy gas oil contained in the unvaporized portion for retreatment in the upper part of the, chamber 23 above the banle 24.

In practicing my invention, a temperature differential is maintained on the oil in the spaces below and above the baille 24. It is essential to maintain a higher temperature` below the baille 24 than above it, this temperature differential generally. being between 10 and 100 F. and in most instances between about 30 and 70 F.' Asl a result of the higher temperature prevailing in the space below the baille 24, heavy gas oil contained in the unvaporized portion of the heavy oil descending into this space from above the baille 24 is vaporized therefrom and passes upe wardly wherein it is further cracked and soaked. In operating with .a temperature differential in the spaces below and above the baille 24, a marked difference in gravity of the oils in these spaces Ahas been found to exist. For example, the heavy oil in the space below thebailie 24 has been 'found to have a gravity of from 2 to 8 A. P. I.

heavier than the oil above the baille and generally between 4 and 6 A. P. I. heavier.

The size of theopening 25 determines the temperature differential in the spaces below and above the baie 24. 'I'his size may -be varied manually before operation is begun, or during oper- ,ation the sam'e effect maybe accomplished by bleeding part of theoil from theA space above the baille 24, such as through part of the` line 3| and line 3|' to the space below the bame 24. If the size of the opening 25 is too large, it is dimcult to maintain the desired temperature differential. The size of the opening should be varied depending upon the conditions of operation and the size of equipment. As an example, with a tower, such as 23, nine feet in diameter, and with 250 bbls. of oil per hour at 1025 F. entering it through the tangential entry 2B, it was found desirable to have an opening 30 inches in diameter.

A substantial body of heavy oil is maintained within the separator and cracking chamber 23. This may be accomplished by maintaining a relatively high liquid level within the chamber, as shown, or the heavy oil may be caused to cascade over suitable baflles 23' against the upwardly flowing stream of vapors.

In some cases it may be desirable not to complete the mild cracking of the heavy oil in chamber 23, in which event, according to a further phase'of my invention a portion of the unvaporized heavy oil`4 is withdrawn from chamber 23 directly above the baille 24 through line 3| and forced by means of pump 32 either to the tubular bank I1 in the convection section of furnace I6 Where it merges with products from the heating coil |2, or a part of the unvaporized heavy oil may be introduced into the transfer line I 9 leading to the reaction chamber 2| in event the latter is employed. Or if desired, a part of the unfvaporized oil may be introduced in line 22 on either side of valve 4|. When part of the nvaporized oil is withdrawn through line 3|, it is generally desirable to provide an extension 30 on baille 24 to prevent vapors from being withdrawn with liquid oil.

Vapors'formed within the separator and cracking chamber 23 Acommingied with cracked vapors liberated therein and remaining uncondensed pass overhead through line 33 to the fractionating tower I3 wherein they are subjected to fractionation and rectification to condense insufficiently cracked products as reflux condensate. To this end the top of the fractionating tower is provided with a suitable trimming coil to regulate the exit temperature of the vapors. If desired, additional reflux, such as nal distillate, may be introduced directly into the top of the tower in lieu of or supplemental to the trimming coil 34.

Fractionating tower I3 is provided with conventional fractionating elements, such as bubble trays, to effect the desired rectification of the vapors. c

Vapors remaining uncondensed in tower I3, Which/,include the sulciently converted constituents, pass overhead therefrom through line 35. provided with a condenser 36, wherein the desired distillate condenses, to a receiving vessel 31 where the desired distillate separates from fixed gases. Fixed gases are withdrawn frorn receiving vessel 31 through line 38 and passed to a gas recovery plant, not shown, and the nal distillate is with' drawn from thereceiving vessel through line 39. I'he desired pressure may be maintained on the coils I2 and I1 and the-reaction chamber 2|, if used, by means of valve 4|. y The pressure maintained on the equipment is not considered critical and may vary over a relatively wide range. The pressure maybe maintained substantially uniform throughout the equipment except f or the necessary differential to effect thedesired flow, or a substantial pressure drop may be employed between the heating coil outlet and the separating and cracking chamber 23.l .In the latter event the transfer line y current contact to said ascending hot gases and 22 is provided with a pressure-reducing valve 4i. The outlet of the heating coil or the outlet of the reaction chamber 2|, in event the latter is used,` may be maintained under a pressure ranging from 400 to 800 or more pounds per square inch, whereas the pressure in the separator 23 and fracl tionating tower I 3 may range from atmospheric to of clean cycle stock from the fractionator is y heated to a temperature of from 900 F. to 1050 F. during passage through the furnace I6 and maintained at cracking temperature for a period adequate to convert from 20 to 40 per cent into con` stituents within the gasoline boiling range during each passv through the furnace. The outlet of the pressure of the coil may be maintained between 100 'and 800 pounds perl square inch. The pressure within the separator 23 may be reduced to from 50 to `100 pounds` per square inch. Reduced crude is introduced into the separator 23 at a rate such that the ratio of fresh charge to cracked vapors is such as' to raise the temperature of the heavy oil above the baille 2l to from about 730 F. to '780 F. with the temperature below the baille 24 being from. about 780 F. to 825 F. The fresh oil is maintained within the Vseparator under cracking conditions for a period sufilcient to accomplish the desired conversion.

Having described the preferred embodiment of my invention, it is understood that it embraces such other modifications and variations as come Within the scope thereof, and it will be further understood thatit is not my intention to dedicate any novel features or unnecessarily limit my invention except as necessary to distinguish from prior art.

I claim:

1. A method for processing hydrocarbon oil -to produce lower-boiling hydrocarbons suitable for motor fuel which comprises subjecting a condensate oil to cracking conditions of temperature and pressure to effect extensive conversion into gasoline hydrocarbons, introducing the resultant cracked products, comprising vaporous and re sidual products of reaction, at cracking temperature into a conned zone below a bafile'in the lower portion of v a reaction chamber in`a stream tangential of the chamber so as to thereby es' tablish and maintain in said conned zone a whirling mass of products promoting a. rapid separation of residual products from vapors and gases which collect about the axis of the whirling mass, withdrawing liquid residual .products from the lower portion of said confined zone, withdrawing the vapors and gases so collecting from said confined zone by passing them through a central opening in said baille and thence upwardly into a body of liquid oil maintained inthe reaction Achamber above said baille while retaining the liquid whirling mass below said `baille, introducing into the upper portion of said reaction chamber and substantially above said haine a hydrocarbon oil heavier than said clean condensate oil wher by said'heavier Voil passes downwardly through said upper portion of said chamber in countervapors, regulating the ratio of said heavier oil to said hot gases and vapors and maintaining contact thereof for a time sufficient' to effect cracking of said heavier oil in said'upper portion of said chamber whereby vaporous and gaseous products of such cracking separate from un- .vaporized oil and pass upwardly with said hot 4 gases and vapors, permitting residual oil from said body of oil undergoing cracking to pass downwardly through said central opening in said baille and into admixture with the whirling mass below the baille whereby said residual oil is quickly raised to a higher temperature to eifect further cracking and vaporization thereof, and fractionating vapors from said reaction chamber to separate a desired distillate product.

2. A method for processing hydrocarbon oil to produce lower-boiling hydrocarbons suitable for motor fuel which comprises passingv a condensate oil through a passageway of restricted cross section in which the oil is heated to a cracking temperature under superatmospheric pressure to effect extensive conversion into gasoline hydrocarbons, introducing the resultant vcracked products, comprising vaporous and residual products ofl reaction, at cracking temperature into a confined zone below a baille in the lower portion of a reaction chamber in a stream tangential of the chamber so as to thereby establish and maintain in said confined zone a whirling mass of products promoting a rapid separation of residual products from vapors and gases which collect about the axis of the whirling mass, withdrawing liquid residual products from the lower portion of said confined zone, withdrawing the vapors and gases so collecting from said confined zone by passing them through a central opening in said baille and thence upwardly into a body of liquid oil maintained in the reaction chamber above said baille while retaining the liquid whirling mass below said baille, introducing into the upper portion of said reaction chamber and substantially above said baille a' hydrocarbon oil heavier than said clean condensate oil whereby said heavier oil passes downwardly through said upper portion of said chamber in countercurrent contact to said ascending hot gases and vapors, regulating the ratio of said heavier oil to said hot gases and vapors and maintaining contact thereof for a time suiiicient to effect cracking of said heavier oil in said upper-portion of said chamber whereby vaporous and gaseous products of such cracking separate from unvaporized oil and pass upwardly with said hot gases and vapors, permitting residual oil from said body of oil undergoing cracking to pass downwardly through said central opening in said baiiie and into admixture with the whirling mass below the baille whereby said residintroduced oil.

` JAMES W. GRAY. 

